The preset invention relates to a device and a method for discriminating cylinders of an engine, and specifically relates to a technique for discriminating cylinders coping with an abnormal time.
As the conventional cylinder discrimination device, there is known such a device in which cylinder discrimination signals of the number corresponding to the number of cylinders are output from a cam sensor during an output of reference crank angle signal from a crank angle sensor, to perform cylinder discrimination (Japanese Unexamined Patent Publication No. 5-106500).
However, in a 6-cylinder engine for example, there is a need to provide to a signal plate for outputting cylinder discrimination signals a maximum of six units to be detected during the output of reference crank angle signal. The problem of this conventional device is that the signal plate cannot be miniaturized, especially for a construction in that a magnetic sensor is used to detect projections formed thereto.
Therefore, there is considered a cylinder discrimination device having a plurality of cam sensors provided in correspondence to a plurality of camshafts, wherein cylinder discrimination is performed during the output of a signal for detecting the reference crank angle position from a crank angle sensor based on the combination of the numbers of signal output from each of the plurality of cam sensors, even when only a small number of units to be detected are formed to the signal plate.
However, according to the above-mentioned cylinder discrimination device, it is necessary to ensure the cylinder discrimination (detection of reference crank angle positions corresponding to cylinders) to be performed in case of failure of the crank angle sensor.
The present invention has been achieved taking into consideration the abovementioned problems and has an object to enable cylinder discrimination to be performed based only on signals output from cam sensors of an engine.
Another object of the invention is to enable cylinder discrimination to be performed using a signal from a crank angle sensor during a normal condition, and to be performed discrimination based only on signals output from cam sensors when the crank angle sensor is malfunctioning.
Moreover, the object of the present invention is to enable cylinder discrimination to be applied especially to an engine where a rotation phase of a camshaft with respect to a crankshaft can be variably controlled in order to variably control the valve timing of intake and exhaust valves.
In order to achieve the above objects, the present invention is constituted as follows.
There is provided a plurality of cam sensors outputting cylinder discrimination signals at every uneven crank angle interval.
A specific cylinder is discriminated based on the cylinder discrimination signals output from the plurality of cam sensors.
Cylinders other than the specific cylinder are discriminated based on the discriminated result of the specific cylinder and the cylinder discrimination signals from the cam sensors.
According to the present invention having the above-mentioned constitution, the cylinder discrimination signals are output from the respective cam sensors at every uneven crank angle interval, so that a specific cylinder can be discriminated for example by measuring the output interval of the signals or counting the number of output of the signals, and moreover, cylinders other than the specific cylinder can be discriminated based on the discrimination result and the cylinder discrimination signals further output from the cam sensors.
According to this constitution, cylinder discrimination can be performed based only on the cylinder discrimination signals from the cam sensors.
Here, the specific cylinder may be discriminated based on the output characteristics of cylinder discrimination signals from another cam sensor during the period of time from the previous output until the current output of cylinder discrimination signals from the respective cam sensors.
According to this constitution, the output characteristics of the cylinder discrimination signals of the plurality of cam sensors can be set so as to be different, for a predetermined time, from the output characteristics of the cylinder discrimination signals from the another cam sensor during the period of time from the previous output until the current output of cylinder discrimination signals from the respective cam sensors. Thereby, the specific cylinder can be discriminated from the other cylinders .
In the above case, the number of output of cylinder discrimination signals from the another cam sensor may be counted during the period of time from the previous output until the current output of cylinder discrimination signals from the respective cam sensors, so that the specific cylinder can be discriminated depending on a difference in the number of signal output.
According to this constitution, by setting the number of output of cylinder discrimination signals output from the another cam sensor during the output interval of cylinder discrimination signals from the respective cam sensors so as to be different for a predetermined output interval, from the other output intervals, the specific cylinder can be discriminated from the other cylinders depending on the difference in the number of signal output.
Moreover, the cycle of input interval of the cylinder discrimination signals may be measured while cylinder discrimination signals output from the respective cam sensor are sequentially input, so that, based on a ratio of the most newly measured cycle and the previously measured cycle, and the discrimination of the cam sensor from which the newest cylinder discrimination signal has been output, the specific cylinder can be discriminated.
According to this constitution, the characteristics of the ratio between the newest value and the previous value of the crank angle interval for every cylinder discrimination signal sequentially output from the plurality of cam sensors can be set so that those of when the cylinder discrimination signals are output from the specific cylinder differ from those of when the cylinder discrimination signals are output from the other cylinders. Thereby, the specific cylinder can be discriminated from the other cylinders based on the ratio between the newest cycle and the previous cycle of cylinder discrimination signal input interval, and the discrimination of the cam sensor.
In the above case, the specific cylinder may also be discriminated when a value obtained by dividing the most newly measured cycle by the previously measured cycle exceeds a threshold value.
According to this constitution, if the newest value/previous value of crank angle interval for every cylinder discrimination signal of cam sensors is set to be greater during the cylinder discrimination signal output corresponding to the specific cylinder than during cylinder discrimination signal output corresponding to other cylinders, the (most newly measured cycle)/(previously measured cycle) value exceeds the threshold value only when the cylinder discrimination signal output corresponding to the specific cylinder. Thus, the specific cylinder can be discriminated from the other cylinders.
Furthermore, the cylinders other than the specific cylinder may be discriminated depending on the number of output of cylinder discrimination signals from a cam sensor corresponding to a cylinder to be discriminated, immediately after the specific cylinder has been discriminated.
According to this constitution, by setting the number of output of cylinder discrimination signals output from a predetermined cam sensor after the output of the cylinder discrimination signal that determines the specific cylinder so as to correspond to each of the cylinders other than the specific cylinder, the cylinders other than the specific cylinder can each be discriminated based on the number of signal output.
Even further, the cylinders other than the specific cylinder may also be discriminated depending on the total number of output of cylinder discrimination signals from the respective cam sensors, immediately after the specific cylinder has been discriminated.
According to this constitution, by setting the total number of output of the cylinder discrimination signals output from all the cam sensors after the cylinder discrimination signal for determining the specific cylinder has been output to correspond to each cylinder other than the specific cylinder, the cylinders other than the specific cylinder can be discriminated based on the total number of output.
Moreover, the constitution may be such that there is provided a crank angle sensor that outputs, in synchronism with the rotation of a crankshaft, a crank angle signal capable of detecting a reference crank angle position for every stroke phase difference between the cylinders, and during a regular condition, cylinder discrimination is performed based both on a reference crank angle position detected based on the crank angle signal from the crank angle sensor and cylinder discrimination signals from the cam sensors, while performing abnormality diagnosis of the crank angle sensor, and cylinder discrimination is performed based only on the cylinder discrimination signals output from the plurality of cam sensors when the crank angle sensor is diagnosed to be abnormal.
According to this constitution, when the crank angle sensor is working normally, the cylinder corresponding to the reference crank angle position can be discriminated to carry out highly accurate engine control (ignition timing control, fuel injection control and so on), while detecting the reference crank angle position with high accuracy based on the crank angle signal output in synchronism with the rotation of the crankshaft. Moreover, the cylinder discrimination can be performed even when the crank angle sensor is abnormal, thus ensuring the necessary engine control.
Further, the constitution may be such that, in addition to the crank angle sensor, there is provided an intake valve timing control device that varies the intake valve timing by changing the rotation phase of an intake-side camshaft with respect to the crankshaft, and when the crank angle sensor is diagnosed to be abnormal, the rotation phase of the intake-side camshaft with respect to the crankshaft is controlled to the most delayed rotation phase.
According to this constitution, when the crank angle sensor is abnormal, the rotation phase of the intake-side camshaft with respect to the crankshaft is controlled to the most delayed rotation phase, to thereby prevent the problems caused when the intake valve timing is controlled toward the advanced angle, such as, the occurrence of knocking during idling state. Moreover, since the rotation phase of the intake-side camshaft with respect to the crankshaft is fixed to a known phase, the reference crank angle position can be detected with high accuracy, enabling to improve the accuracy of a fail-safe control.
Moreover, the constitution may be such that, in addition to the crank angle sensor, there is provided an exhaust valve timing control device that varies the exhaust valve timing by changing the rotation phase of an exhaust-side camshaft with respect to the crankshaft, and when the crank angle sensor is diagnosed to be abnormal, the rotation phase of the exhaust-side camshaft with respect to the crankshaft is controlled to the most advanced rotation phase.
According to this constitution, since the rotation phase of the exhaust-side camshaft with respect to the crankshaft is controlled to the most advanced rotation phase when the crank angle sensor is abnormal, the problems caused by the exhaust valve timing being controlled toward the delayed angle, such as, knocking caused during idling condition, can be prevented. Moreover, since the rotation phase of the exhaust-side camshaft with respect to the crankshaft is fixed to a known phase, the reference crank angle position can be detected with high accuracy, enabling to improve the accuracy of the failsafe control.
Even further, the cam sensors can each be mounted respectively to each bank in a V-type engine, or they can each be mounted respectively to each camshaft in an engine equipped with an intake-side camshaft and an exhaust-side camshaft.
According to these constitutions, the cylinder discrimination is performed based on the combination of the number of cylinder discrimination signals being output from a cam sensor mounted to one camshaft between reference crank angle positions and the number of cylinder discrimination signals being output from another cam sensor mounted to the other camshaft between reference crank angle positions. In this way, since two cam sensors are mounted to different camshafts, the length size of the camshaft can be designed smaller compared to when two cam sensors are mounted to one camshaft.
The other objects and features of the present invention will become understood from the following description with the accompanying drawings.